In order to transport bulk materials, such as coal, iron ore, and other minerals, the mining and other industry uses Off-The-Road (OTR) vehicles that may weigh up to 670 tons when fully loaded. As a result, extremely high internal stresses are imposed on the tires of such vehicles in the course of their daily use. Such internal stresses are proportional to the speed at which the vehicle is driven and excessive speed can result in a destruction of the vehicle tires. Consequently, the speed of an OTR vehicle is controlled on the basis of the operator's perception of the condition of the tires at any given time. Accurate information regarding the tires, particularly its pressure and temperature, is therefore essential in order to assist the operator and avoid damage to an OTR vehicle's tires. It is, therefore, advantageous to provide a tag for measuring OTR vehicle tire pressure and temperature and communicating such information to the operator.
Because of the extremely rigorous operational and environmental conditions in which OTR vehicle's operate, a suitable tag must, in addition to being accurate, be durable and of high structural and operational integrity. In the environment in which the OTR vehicles operate, it is not uncommon for foreign material to invade the tire air cavity. Such material along with anti-corrosive liquid can be abrasive and cause damage to the tag transmitters and contaminate the electronics, leading to premature failure of the tag.
Various attempts have been made to monitor the tire condition in an OTR vehicle and to provide operators with timely information concerning such conditions. For example, U.S. Pat. No. 6,255,940, incorporated herein by reference, teaches apparatus for monitoring tire condition and includes a tag housing and a patch having a first side for mounting against the inner liner of the tire and a second, arcutately-shaped side and an internally threaded socket member. A threaded steel assembly bolt is made to extend from a side of the tag housing and into the threaded socket of the patch. The tag housing includes means for measuring temperature within the tire cavity through measurement of the temperature of the steel assembly bolt. Additionally, pressure is measured by the tag and the temperature and pressure data are transmitted to an external processor and display.
While the apparatus in the aforesaid patent works well and represents an advancement over prior art, the industry remains in need of apparatus for a tire monitoring system of still greater durability and resistance to damage from environmental contaminants. Moreover, still greater accuracy than that achieved heretofore in the measurement of temperature and pressure conditions within an OTR tire is desired. Deducing the temperature of the tire cavity through measurement of the apparatus bolt, as taught in the prior art, is inherently less than precise.